Spark plug with sleeve-constrictive bushing



Sept.29, 1931. 'H.RABEZZANA 1,825,362

SPARK PLUG WITH SLEEVE GONSTRICTIVE BUSHING Filed Dec. 7, 1928 Patented 193.1

HECTOR RAIBEZZANA, OF FLINT, MICHIGAN, ASSIGNOR TO PANY, OF FLINT, MIGHIGAN A COMPANY OF A sranx PLUG COM- MICHIGAN SPARK PLUG SLEEVE-CONSTRICTIVE BUSHING Application filed' December 7, 1928. Serial No. 324,511.

This invention should be understood to relate not only to novel mica-containing or simila laminated-insulation s ark plugs but to means and methods of ma ng and asso- 5 ciating parts appropriate to so-called onepiece or permanently-assembled spark plugs, of the type referred to. i B

It is a general object ofthis invention to provide superior spark plugs, including mica-insulated or like spark plugs'which are suitable for use upon air craft; said plugs may typically include central electrodes upon whose conductive stems inner and/or outer mica assemblies are secured, under suitable compression and in leak-preventing relation ship, by means comprising special joints provided by inwardly collapsible intermediate bushings and/or terminal stop elements; in preferred embodiments, the stems of the mentioned centr'al electrodes may carry insula tion sleeves, adapted to extend through one or both of the mentioned assemblies and optionally to be placed under high radial compression by an inward collapse of weakened zones of the mentioned bushings; and the present invention contemplates also a novel technic for use in securing this bushing (or another I suitable bushing-preferably afteritsinward collapse) within asuitably threaded or other shell or metallic body,the latter being preferably adapted to receive and to retain under axial compression an auxiliary sheaf of mica insulation and to undergo, in an intermediate weakened zone, an inward deformation.

Any or all of the mentioned deformations may be effected thermo-plastically and without injuring, by radial compressions or otherwise, any of the mica or other (presumably non-vitreous) insulation employed; as in my application S. N. 324,513, filed December 7, 1928, each inner electrode element may 1nclud'e, at oneend. an integral head which pro- I vides an upwardly or inwardly facing shoulder, adapted to serve as a stop element for the retention of a sheaf of mica washers, or the like, comprisedv in an inner assembly; and use may be herein made of a special threadless collapsing nut, the bore thereof being preferto assure engagement or partial ably such as or the like, uponthe stripping of any threads,

stem of said electrode, to a welding effect by bly may be secured. V

- As in the mentioned application, each mica assembly upon the central electrode stem may include a small-apertured or electrode-fitting layer or sheaf of mica washers and a largerapertured or tube-receiving sheaf thereof; but the lower or inner mica assembly may which the outer assemherein be partially received within a suitable recess in the intermediate bushing and/or supplemented by the-use of an auxiliary sheaf of mica washers, surrounding but. not in contactwith the mentioned, head and seated within the mentioned threaded body, somewhat as described and claimed in my application S. N. 324,512, filed December 7, 1928.

The mentioned threaded be provided not only with cavity adapted to receive said auxiliary layer but with a tapered or other continuation; and this may be specially shaped to keep the same spaced from, and thereby obviate danger of damage to, said lower or inner mica assembly during any local application of heat and of such longitudinal pressure to said shell or threaded body as may be employed in an optional final deformation of a weakened zone thereof. Foregoing radial constriction of the insulating washers, this construction is effective axially to compress and permanently to secure one or more of said mica assemblies;

and any desired mechanical shaping or otheroperations may be either prevlously or subsequently executed upon a part or parts of the external mica assembly,-a special packing being optionally interposed, in advance of the mentioned deformations, shoulders provided by metallic or other parts referred to. a

The mentioned outer assembly may be secured either before or after or incidentally to the last-mentioned deformation; but the mica body or shell may a cylindrical conbetween opposing in a manner favorable compacting pressures employed are preferably less than the deformation pressures; and other objects of this invention, including various details of method and of mechanical means and of leak-obviating structure (all aiming at superior durability and reliability in use and/ or at economy and efliciency in production) may be best appreciated in the following description of an illustrative embodiment thereof, taken in connection with the appended claims and the accompanying drawmgs.

Fig. 1 is a vertical sectional view through one form of permanently-assembled spark plug made in accordance with this invention.

Fig. 2 is a vertical section showing an inner electrode element as provided with an inner composite assembly of mica insulation, this being interposed between and adapted to be retained by a shouldered head and a novel inwardly collapsible intermediate bushingdies suitable for use in an application of pressure to compress said insulation and then collapse said bushing being shown as broken away.

Fig. 3 is a diagrammatic vertical sectional view, illustrating a preferred means and method for securing the parts shown in Fig. 1 under a desired compression the mentioned bushinsfi-some parts being broken away and certain optional operating and control parts being partially indicated upon a reduced scale. 7

Fig. 4 shows, partially in vertical section, a second or outer mica assembly and a Collapsible retaining nut of so-called air craft type.- the latter being positioned. out-wardly of or above the mentioned bushing and above said assembly, upon the inner electrode stem element.

Fig. 5 is a view comparable with Fig. 3 but illustrating the collapse of the mentioned nut, for a securing effect.

Fig. 6 is a vertical sectional view illustrating a step of seating and/or compressing an auxiliary sheaf of mica insulation within a special threaded shell or grounded-electrode body, this being adapted to receive a part of said bushing and interior assembly.

Fig. 7 is a view. somewhat-similar to Figs. 3 and 5, but showing more particularly alternative or final steps involved in permanently assembling a special externally-threaded plug body relatively to a double-insulated main electrode unit or spindle comprising a collapsed or other intermediate bushing and additional parts of the general character referred to,-an.auxiliary mica sheaf being incidently placed under a desired compression.

In Figs. 1 and 7. thoseparts which are shown in elevation in Fig. 7 may be referred to as constituting a composite or double-insulated main electrode spindle or unit; and in this in-' stance, as in one of the mentioned applications, an intermediate bushing 10. comprised in said' spindle, is shown as inwardly collapsed relatively to a sleeve 11 (formed of mica or other suitable insulating material. a metallic tube 12 being optionally interposed) in such manner as not only to form a substantially gas-tight joint or sealing at 13 but also to retain,

under a desired compression, an mby collapse of terior assembly of mica. The latter may comprise a small-apertured sheaf 14, adapted to receive an electrode stem 15, and a largerapertured sheaf 16, adapted to fit over said sleeve, both of said sheaves being held under compression between said bushing and a stop element such-as a shouldered head 17 on said electrode stem. Said tional insulation such as an exterior mica assembly comprising a large-apertured sheaf 18 and a small apertured sheaf 19, these being retained under compression by any suitable nut 20; and the exposed parts last referred to may advantageously be trimmed to frustoconical or similar form (as by means of a lathe) and polished, he mica sheaves then appearing translucent and lustrous.

In the present instance, the interior mica assembly is shown as externally cyindrical and as seated within a wedge-fitting or other concavity 21, optionally provided in the bushing 10: and the nut 20 is shown as of socalled air craft type. This nut, or any preferred mica-retaining stop, may be collapsed upon a close-fitting or partially stripped threaded portion 22 of the electrode stem 15,-the illustrated nut being provided with a connection-receiving channel '23, partially defined by a terminal and flat flange 24, and with a reduced-section portion; and the bushing 10 is shown as provided, below an upper or pressure-transmitting flange 25 and a weakening annular channel 26 (diminished by, but optionally permitted to sur- "ive, a collapsing operation hereinafter referred to) with (1) a downwardly-expanding body providing a rounded shoulder or surface 27 (for engagement by a deformed locking flange upon a surrounding shell or body) and with (2) a cylindrical surface 28,--the latter terminating in a flat shoulder 29. Assuming the bushing 10 to be unprovided with external threads, the present invention contemplates the use, with the described insulated electrode spindle or an equivalent unit, of an outer or grounded-electrode shell or body B, which may be of special design. The illustrated outer body B comprises a flat-flanged portion 30 and a non-circular wrench-receiving portion 31,-the latter including a mentioned bushing-lock flange 32 and an inner shoulder 33, and the portions 30 and 31 being preferably spaced apart by a constriction. Shoulder 33 may directly opose the mentioned shoulder 29, upon the ushing 10; and leak-preventing meanssuch -as copper-asbestos gaskets 34 may be interposed between two or more opposed surfaces stem may carry addi-.

such as these provided by the mentioned shoulders 29 and 33.

It will be seen that the flange 32, when inwardly bent or extended, locks the bushing 10, and thereby the described spindle orits equivalent permanently within a suitable concavity in the wrench-receiving portion 31;

' tion annular region 39 bly, (2) relia of any of and an insulation chamber is shown as extending downwardly therefrom. The latter chamber need not be uniformly cylindrical throughout. It preferably comprises not only a cylindrical or very slightly tapered lower portion 35 (shown as extending into a region which is provided with external threads 36, and as adapted to receive an auxiliary and compacted sheaf 37 of interfitting mica Washers, or the like) but also a wider or tapered intermediate portion 38. This is shown as downwardly continuous with the portion 35; and the mica washers which comprise the auxiliary sheaf 37 may be of the same external diameter as the sheaf114 and or the sheaf 16,-the result being an upwardly increasing clearance, about sheaves 14 and/or 16, which enables sheaf 14, if desired, and/0r sheaf 37 to be given a wedging or-drive fit. Destruction of this sheaf, in use, does not ruin the plug.

The foregoing construction is rugged and diirable, and it substantially obviates leakage,obvious'additional advantages of the mentioned ta er being (1) facility of assemle transmission of compression thrust to sheaf 37 during final stepsof assembly, and (3) avoidance of any distortion the mentioned sheaves (as sheaf 16) as a result of any radial pressure arising from an inward bulging which may occur, as at 39, opposite a constricted or reduced-secwhich is preferably provided between the respective portions 30 and 31 of the threaded shell or body,to permit of an application of pressure to some or all of the mentioned sheaves and especially to auxiliary sheaf 37 (through nut 20 and/or the bushing 10 and the sheaves 14 and 16) presumably after the gasket 34 has under gone a desired compression and the flange 32 has been given (thermoplastically or otherwise) substantially the form shown in Fig. 1. (4} Good thermal conductivity is also obtained.

in regard to methods of manufacture, although reference may be made to the application first above mentioned for one sequence of steps available in the production of the double-insulated spindle or unit such as is shown in elevation within Fig. 7 and 'although the entire unit referred to, or'its equivalent, might be formed by any desired alternative steps (as, by a lose assembly of mentioned parts in coaxial relationship upon an electrode stem, followed by successive ad-' vances of dies such as are suggested at 40 and 41, Fig. 7, relatively to a pressure-limiting die 42 and a fixed die 43) the present invention may be regarded as including a preferred and novel method wherebysome or all of the mica sheaves 14, 16, 18, and 19 may be subjected, during assembly; only to pressures less than that or thos employed in effecting the col-lapse of redu ed and momentarily elements directly softened zones in metallic retaining elements,such as the bushing 12, the nut 20, and/or a weakened zone and/or flange of the described external shell or body B. But it will be understood that some or all of said *ins'ulationmay be finally subjected to a high axial pressure, due to thermal contraction of said shell.

Formation of electrode head 17 integral with the stem 15 may approximately predeterm'ine a sequence of assembly of the mica sheaf 14, the sleeve 11, the sheaf 16, the tube 12, and the bushing 10; but it will be recog nized as practicable either to dispose these upon said stem or to transfer the same thereto from a suitable arbor; and in any case, the head 17, or its equivalent, is preferably supported by means such as a yieldable plunger 42 or 42, shown as movable within fixed die 43 or 43; and the relationship between the parts last referred to may be such as to necessitate the limited advance of an upper and movable die 44 or its equivalent, compressing the mica assemblies 14 and 16 to a desired extent, before an engagement of the bushing 10 with the fixed die 43 can occur or result in a sufiicient longitudinal or axial compression of said bushing to effect an inward collapse of any constricted portion 45 thereof. For example, the plunger 42, .may be provided with a chamber 46 adapted to receive compressed air, .or the like, through an interfitting fixed element 47, provided with a passage 48, the latter communicating with a compressed air source 49 by means of a passage 50 provided with a pressure-limiting valve 51. This valve -may be set at, for example, 2000 pounds, while something like twice that pressure may be employed in advancing the movable die element 44, or its equivalent. The die 44 may be ad- Vance either by any ordinary mechanical means or by hydraulic means, either means being optionally under the control of an air valve 53, manipulable by means such as a rod 54. The bushing 10 having engaged die 43 or 43', any desired means, such as a suitable electric current provided from a source 55, may be employed to occasion collapse thereof by momentarily heating the reduced section 45 of bushing 10 after a desired pressure has been applied therethrough by the described meansor equivalent means; and a handle 56 is shown as adapted not only to manipulate the rod 54 but to open and close a switch 57,

optionally included in the circuit compriscraft type nut 20 (shown as locally so reduced, at 59, as to occasion a resistance favorable to heating) to have been applied to the threaded section 22 of the stem 15 after the positioning of the exterior insulation as-' sembly comprising mica sheaves 18 and 19 thereon, similar means comprising the die 4.0 or 40 (affording protection to channel '23 and flange 2 f) may be employed to collapse the reduced-section zone 59 of said nut and to auxiliary mica assembly 37 within any concavity 35 provided in the threaded portion 30 of the exterior body, in advance of an insertion of both the packing ring 34, or its equivalent, and the double-insulated spindle or unit above described, or any preferred unit, for compression and retention in the general manner best indicated in Fig. 7. I

Insulation .is vdiagrammatically suggested at 61 in various figures and, in Fig. 7 (which incidentally discloses means whereby all mentioned deformations might beetfectedl the flange 32 is shown as engaged by the movable die 41; and it will be understood that, although only a moderate pressure may have been applied to the auxiliary mica assembly 37 either through plunger 60 or through the mica sheaves 14 and 16 and parts thereabove,

at least a. part of a final pressure is prefe rablyapplied after the flange 32 becomes inwardly deformed,-as, by a continued but slight descent of the die 41 to a position below that indicated bythe dotted line 41 and/or by a subsequent cooling,-suificient pressure for a slight and presumably final collapse of the reduced section 39 of the mentioned threaded body being preferably applied for a thermoplastic effect, during an electrical heating timed with reference to an advance of one or both of the dies thereabove.

In view of the tapered or other non-contacting surface provided at 38, a collapse at 40 may be so executed that any 39 shall not separate or injure any of the previously compressed sheaves of mica, even if said bulge should touch tecting element being interposed. Upon cooling the shell B naturally exerts increasing compression effects upon at least the sheaves 14, 16. and 37; but such effects could be transmitted to sheaves 18 and 19 only in case bushing 10 were incompletely collapsed.

Although I have herein described but a single embodiment of the present invention, suggesting various alternative details of construction and of method, it should be understood not only that various features of this invention may be capable of independent use and that thermoplastic effects may be utilized in connection with any or all of the mentioned collapses,

inward bulge the same, no probut also that numerous additional modifications might easily be devised,-all

without involving departure from the scope of this invention as the latter is indicated above and in the following claims. I

I claim:

1.. In a spark plug including non-vitreous insulation: an electrode spindle unit comprising inner and outer insulation assemblies separated by a constrictive bushing; and a shell providing a chamber for said spindle, a deformed retainer flange engaging said bushing and a seat for an auxiliary sheaf of non-vitreous insulation held under compression through said inner insulating assembly.

2. In a spark plug including non-vitreous insulation: an electrode spindle unit comprising inner and outer insulation assemblies separated by a constrictive bushing; an a shell providing a chamber for said spindle, a deformed retainer flange engaging sai bushing and a seat for an auxiliary sheaf of non-vitreous insulation held under compression through said inner insulating assembly.said shell being provided with a deformation zone laterally spaced from said inner assembly.

3. In a spark plug: a shell provided with deformation zone and internally providing an insulation chamber which downwardly terminates in a seat, an auxiliary sheaf of non-vitreous insulation on said seat: and an inner insulation assembly surrounding an electrode and held under axial compression on y,said chamber being tapered toward said seat.

4. In a spark plug: a a deformation zone and internally providing an insulation chamber which downwardly terminates in a seat for an auxiliary sheaf of non-vitreous insulation: and an inner'insulation assembly surrounding an electrode and held under axial compression only,said chamber being tapered toward said seat, and said auxiliary sheaf having a drive fit with the wall,of said chamber. v

5. In a spark plug: a shell provided with shell provided with a deformation zone and internally providing an insulation chamber which downwardly. terminates in a seat for an auxiliary sheaf of non-vitreous insulation: and an inner insulation assembly surrounding an electrode and held under axial compression only,said chamber being tapered toward said seat, and said auxiliary sheaf having a drive fit with the wall of said chamber and being of substantially the same diameter as said inner assembly.

6. In a spark plug includingnon-vitreous insulation: an electrode spindle unitcomprising inner and outer insulation assemblies separated by a collapsed bushing; and a shell providing a chamber for said spindle, a flange engaging said bushing and a seat for an masses auxiliary sheaf of non-vitreous insulationr held under compression through said inner insulating assembl ,--said shell being provided with a de ormation zone laterally spaced from said inner assembly, and said bushing and said shell being provided with substantially flat and opposed faces between which a gasket is interposed favorably to a transmission of a compression thrust to said deformation zone.

7. In a spark plug including non-vitreous insulation: an electrode spindle unit comprising inner and outer insulation assemblies separated by a collapsed bushing and a shell providing a chamber for said spindle, a flange engaging said bushing and a seat for an auxiliary sheaf of non-vitreous insulation held under compression through said inner insulating assembly,said shell and said bushing being interlocked by a deformation of a part of said shell on said bushing.

8. In a spark plug including non-vitreous insulation: an electrode spindle unit comprising inner and outer insulation assemblies separated by a collapsed bushing and a shell providing a chamber for said spindle, a flange engaging said bushing and a seat for an auxiliary sheaf of non-vitreous insulation held under compression through said inner insulating assembly,-said shell being externally provided with a non-circular portion and with a flat-flanged portion, and said portions having a deformation zone therebetween.

9. For use in a spark plug comprising laminated insulation compressed within a shell, a bushing comprising: a pressure-receiving flange element; and a rounded flangereceiving element,said elements being sepaof reduced cross section. a

10. For use in a spark plug comprising laminated insulation compressed wlthin a shell, a bushing comprising: a pressure-receiving flange element; and a rounded flangereceivin element,said elements being se arated y a thermoplastically deformable zone of reduced cross section. J 11. For use upon a spark plug comprising mica insulation: an air-craft type nut comprising a connection-receiving flange a pressure transmitting flange; and a body therebetween which is provided with a zone'of re duced cross section, the interior diameter of said nut being favorable to its thermoplastic collapse at said reduced zone upon the application of longitudinal pressure on the nut. 1

12. For use in a spark plug comprising mica insulation: a receptacular shell provided with a zone which is adapted to a thermoplastic collapse and with an insulation-receivlng chamber so shaped as to space said zone from insulation compressed by such colla se. 65 13. For use in a spark plug comprisingpredetermined pressure,

rated by a thermoplastically deformable zone mica insulation: a receptacular shell rovided with a zone which is adapted to a t er moplastic collapse and-with an insulationreceiving chamber so shaped as to space said zone from insulation compremed by such collapse,'said chamber being tapered and adapted to receive both the insulation. so spaced and an auxiliary assembly which snugly fits therebelow and is held compressed through said first-mentioned insulation.

14. In means for securing an insulation assembly under a predetermined compression uponaconductive element which provides a stop therefor and carries an inwardly collapsible retaining element: a movable die element adapted to engage said-collapsible element; a die element engageable by said collapsible element; an additional die element adapted movably to receive said insulation assembly; and means yieldable under a predetermined pressure, for supporting said additional die element during advance of said movable die element.

15. In means for securing an insulation-assemblyunder a predetermined compression upon a conductive element which provides a stopv therefor and carries an inwardly collapsible retaining element; a movable die element adapted to engage said collapsible element; a lixed' die element engageable by said collapsible element; an additional die element adapted movably to receive said insulation assembly; means, yieldable under a Y for supporting said additional die element during advance of said 100 movable die element; and means for softening a zone of said retaining element favor- Tably to a collapse and subsequent contraction thereof,

16. In means for securing an insulation 83- 108 sembly under a predetermined compression uponwa conductive element which provides a stop therefor and carries an inwardly collapsible retaining element; a movable die element adapted to engage said. collapsible 110 element; a nxed die elementengageable by said collapsible element; an additional die element adapted movably to receive said insulation assembly, means yieldable under a predetermined pressure, for supporting said 115 last mentioned die element during advance of said movable die element; and means for softening a zone of said retaining element favorable to a collapse thereof, said softening means being electrical and being operative upon a predetermined advance of said movable die element.

17. In means for securing mica insulation under a predetermined pressure upon a con ductiveelement and between a stop element thereon and. a collapsible retaining element; means, yieldable under a predetermined pres- .sure, for supporting said stop element; and

means, operative upon the yielding of said stop element, to collapse said retaining element.

18. In the production of a permanentlyassembled mica-containing spark plug, a method which comprises: assembling an insulating unit by securing an interior mica assembly and an exterior. mica assembly both under compression upon an electrode and on opposite sides of an intermediate bushing, said bushing being collapsed thereon and comprising a shoulder; and securing the insulating unit partiallywithin a body, provided with a cooperating shoulder and with a flange, by opposing said shoulders and collapsing said flange.

19. In the production of a permanentlyassembled mica-containing spark plug, a

method which comprises: assembling an insulating unit by securing an interior mica assembly under compression and on an electrode and between a head thereon and a collapsed bushing; disposing auxiliary insulation in a shell; and securing the insulating unit partially within said shell, after an application of axial pressure to said auxiliary insulation through said unit,-said shell being deformed into a locking engagement with said bushing.

20. A method as defined in claim 19 in which said shell being provided both with a flange adapted to be deformed to engage said bushing and with a weakened zone which is subject to a thermoplastic collapse, said flange is deformed into such engagement and said zone is subsequently so collapsed, while heated, as to assure high compression and gas-tight engagement between adjacent parts.

In testimony whereof I afiix my signature.

HECTOR RABEZZANA. 

